This invention relates to an operating arm attached to an earth-moving or foundation machine and guiding different tools, which consists of an upper arm pivotally connected directly to the machine or via a boom, a lower arm pivotally connected to the upper arm and carrying the tool, and with a drive which moves the upper arm and the lower arm from an extended position via a folded position, in which both arms are side by side, into an oppositely extended position.
An operating arm of this type with an excavator bucket is known from German Offenlegungsschrift No. 3,106,268 of the applicant. By means of a multi-element linkage pivotally connected to the boom and connected to the upper arm, the operating arm guides the excavator bucket on a curved forced path to the dumping spot and back along the same path to the excavation area. A disadvantage with this arrangement is that the direction of the forced path can only be changed by rotating the boom up or down and that the curvature of the forced path is determined by the linkage and unalterable. In addition, no exactly straight-line path can be achieved by means of the linkage. These disadvantages hinder multi purpose applications.